What is Greywater?

Water conservation in California with our summer-dry climate is nothing new. The best approach is to landscape with plants that are already adapted to our long dry summers and need only occasional watering during the dry season. The other conservation option is a greywater irrigation system.

Why are we hearing so much about this now? Until recently, greywater systems were not a legal option for single-family homeowners in California. In July of 2009 the State of California officially incorporated greywater standards into their building code.

Greywater Sources
Greywater systems use non-potable (not drinkable) water for landscape, such as rainwater or drain-water from laundry, bathroom sinks, tubs, and showers. During the rainy season we can catch and use the rainwater from our roofs, but during the dry months we need other sources of landscape water. Water from the kitchen sink or dishwasher is not legal greywater because the high concentration of organic compounds can create a potential health hazard.

Greywater systems range from extremely simple to highly complex. Most useable residential greywater comes from the tub/shower and laundry. Conversion of existing bathroom plumbing requires professional replumbing, and may be impossible with a slab foundation. A washing machine, on the other hand, can be easily replumbed by a do-it-yourselfer.

Laundry to Landscape
Oasis Design has been at the forefront of design and policy regarding greywater systems since 1980. Laundry to Landscape is their program with free information on how to do a simple laundry-only system. It is the simplest, most economical residential greywater system that gets the most greywater out on to the landscape. Their website www.oasisdesign.net is a wealth of information on the history, policy, design and installation of greywater systems.

When Not to Use Greywater
There are a number of possible reasons not to use greywater or to use it only during certain times of year. Obviously, if you get year-round rain you don't need any kind of landscape water. Some homes don't have enough space, or don't require enough landscape water to justify the trouble and expense of installing the system. The main reasons greywater remains illegal in many areas is concern for public health. However, in practice, the health threat from greywater has proven to be insignificant.